This invention relates to electrical energy power supplies and more precisely, to specialized batteries which have special utility in packs or assemblies comprising a container holding self-developing film units integrated with a battery power supply.
U.S. Pat. Nos. 3,705,542; 3,543,662; 3,543,663; and 3,595,661 relate to photographic film packs comprising an enclosure containing self-developing film units integrated with a power supply system. Such film packs are presently employed exclusively in a highly automated photographic camera sold by Polaroid Corporation of Cambridge, Massachusetts, U.S.A., under the trademark "SX-70".
Essentially, film packs or cassette structures described in those patents are of a disposable nature and comprise an opaque enclosure containing a dark slide for covering an exposure station in a forward wall of the container, a stack of individual "self-developing" film units described, for instance, in U.S. Pat. No. 3,415,644 and others, positioned behind the dark slide, means for urging the stack of film units towards the forward wall to position the uppermost film unit in the stack in the exposure station and a battery power supply for powering electrical mechanisms of the camera designed for using the pack.
A photographic cycle for the above-noted camera involves a somewhat complex series of operational events each imposing electrical power demands and each being controlled by an integrated solid state control circuit. As detailed in U.S. Pat. No. 3,774,516, this control circuit monitors several mechanical manipulations of the instrumentalities of the device involving a dual energization of a d. c. dynamoelectric motor as disclosed in U.S. Pat. Nos. 3,791,278; 3,750,543, 3,805,204 and 3,820,128. The operational events carried out by the camera include those of securing an exposure chamber, reflux optical path conversion, exposure regulation of a film unit, motor driven film unit removal and processing as well as the noted automatic dark slide removal.
To power the camera throughout a series of the above-catalogued operational events, a battery power supply is required which exhibits a low internal impedance and is capable of providing a relatively high current output with multi-cycle capacity. During its powering activity, the battery is called upon to maintain the predetermined voltage levels required for operating integrated logic control circuits.
A particularly desirable attribute of the noted camera-film system resides in the foldability of the camera component thereof into a thin, compact configuration suited for facile portage. The availability of such design compactness stems, in part, from the utilization of a flat battery structure in combination with the film cassette for the power supply of the camera. Of considerable importance to the system, however, by providing a battery which is discardable with an exhausted film cassette, the camera operator is assured of the presence of a fresh power supply upon each replenishment of a film supply to the camera. Essentially, the film pack contained power source has comprised a battery of the type described in detail in U.S. Pat. Nos. 3,543,662; 3,563,805; 3,617,387 and 3,734,780 among others. These flat or planar batteries are primary batteries of the LeClanche type including a zinc anode system, a manganese dioxide cathode system and an aqueous electrolyte of ammonium chloride, zinc chloride and usually a small amount of mercuric chloride. When the film pack is inserted into the camera, the battery integrated therewith is connected to the camera's electrical system to provide a power source of sufficient current capacity and evidencing requisite low internal impedance for operating the camera through a given number of cycles, for instance, ten. When all film units in the pack are exposed and automatically transported from the camera, the pack -- containing the integral battery -- is discarded.
As described in copending application for U.S. Pat. Ser. No. 411,254 filed Oct. 31, 1973 entitled "Electronic Photographic System" by E. H. Land and assigned in common herewith, it is highly desirable that the thin flat batteries, while still remaining fabricable at a unit cost permitting them to be discarded following the expenditure of the film supply, be capable of providing the power required to charge the capacitor of an electronic flash unit. This current drain capability should be such as to permit recharging over the requisite number of cycles at a relatively rapid rate, for instance, within an interval averaging about 5 seconds. The charging capability for the discardable batteries should be suitable for photographic system energy requirements of, for example, about 100 watt seconds for each photographic cycle.
As alluded to above, such batteries must be compact and specifically configured for effective integration and assembly with the film pack and at the same time provide requisite electrical energy for efficient operation of the camera and related accessories until depletion of the supply of film units in the film pack. Inasmuch as the film-battery combination is designed to be discarded following film supply exhaustion, an economic constraint is involved requiring that the batteries be produced using high volume, low cost procedures which inevitably dictate the involvement of a manufacturing process capable of efficiently assembling batteries and providing maximum production of acceptable batteries with minimum rejects.
In copending applications for U.S. Patent, Ser. No. 495,681 by S. A. Buckler filed Aug. 8. 1974; and Ser. No. 495,628 by E. H. Land, filed Aug. 8, 1974, both applications being assigned in common herewith, flat primary batteries highly suited for the noted photographic application and, particularly, which exhibit current drain capacities for applications providing for the powering of such accessories as electronic flash units are described. One feature of such batteries resides in the formation of at least one cell electrode thereof having a slurry of active particulate material dispersed in aqueous electrolyte. In the latter of the above-identified applications, for instance, a preferred multicell planar primary battery is described in which each positive electrode is formed including a planar cathode current collector carrying on one surface, in order, a first cathode mix comprising a particulate dispersion of cathode mix particles in a binder matrix and a second slurry-type cathode mix comprising a particulate dispersion of cathode mix particles disposed within aqueous electrolyte. The multicell planar batteries incorporating the particulate active material generally include sheet intercell connectors and separators along with border sealing means which are appropriately combined intermediate terminal defining end cathode and anode current collector subassemblies to define pile structures.